Drought Study Shows Risks to Colorado River’s Water Supply

A new study underscores the importance of water from Colorado's West Slope basins, which supply seven western U.S. states, including critical water deliveries to Lake Powell. However, the research warns that even under moderate climate projections, these basins may face a tipping point where traditional water delivery levels become unsustainable.

Published in Earth's Future, this study is the most comprehensive analysis to date of drought vulnerability in the basins, which are made up of six key watersheds feeding into the Colorado River. These watersheds support a $5 billion agricultural economy and are essential for maintaining Lake Powell's water levels. The findings come at a crucial moment as water-sharing agreements between states and the federal government are set to expire soon.

The study, led by Patrick Reed of Cornell Engineering, aimed to explore the limits of current water management policies and identify areas where new strategies could help ensure sustainability. By combining Colorado’s StateMod planning model with a novel hidden Markov modeling framework, the team created thousands of streamflow scenarios under both historical conditions and future climate projections.

Results show that relying solely on historical streamflow data for drought analyses could seriously underestimate the severity and impact of future droughts, particularly on water storage, agriculture, and municipal water supplies. The study suggests that even small changes in climate and streamflow could push these basins past a tipping point, making it difficult to maintain current water deliveries to Lake Powell.

In 2021, a significant drought caused Lake Powell to reach historically low levels, leading to the first-ever water shortage declaration by the U.S. Bureau of Reclamation. The study reveals that such shortages can occur due to internal variability in the basins, even without the influence of climate change, and that drought impacts are interconnected, straining the entire system.

The study’s lead author, David F. Gold, stresses the need for advanced drought analysis methods that capture these widespread, interconnected impacts. He argues that with increasing pressure on water resources, integrated, scientifically informed management approaches are essential for maintaining resilience in complex river basins, both in the U.S. and globally.